Project description:The construction and operation of a novel viscometer/rheometer are described. The instrument is designed to measure the viscosity of a macromolecular solution while automatically varying both solute concentration and shear rate. Viscosity is calculated directly from Poiseuille's law, given the measured difference in pressure between two ends of a capillary tube through which the solution is flowing at a known rate. The instrument requires as little as 0.75 mL of a solution to provide a full profile of viscosity as a function of concentration and shear rate, and it can measure viscosities as high as 500 cP and as low as 1 cP, at shear rates between 10 and 2 × 10(3) s(-1). The results of control experiments are presented to document the accuracy and precision of measurement at both low and high concentration of synthetic polymers and proteins.
Project description:One of the most challenging aspects in the molecular simulation of proteins is the study of slowly relaxing processes, such as loop rearrangements or ligands that adopt different conformations in the binding site. State-of-the-art methods used to calculate binding free energies rely on performing several short simulations (lambda steps), in which the ligand is slowly transformed into the endstates of interest. This makes capturing the slowly relaxing processes even more difficult, as they would need to be observed in all of the lambda steps. One attractive alternative is the use of a reference state capable of sampling all of the endstates of interest in a single simulation. However, the energy barriers between the states can be too high to overcome, thus hindering the sampling of all of the relevant conformations. Accelerated enveloping distribution sampling (AEDS) is a recently developed reference state technique that circumvents the high-energy-barrier challenge by adding a boosting potential that flattens the energy landscape without distorting the energy minima. In the present work, we apply AEDS to the well-studied benchmark system T4 lysozyme L99A. The T4 lysozyme L99A mutant contains a hydrophobic pocket in which there is a valine (valine 111), whose conformation influences the binding efficiencies of the different ligands. Incorrectly sampling the dihedral angle can lead to errors in predicted binding free energies of up to 16 kJ mol-1. This protein constitutes an ideal scenario to showcase the advantages and challenges when using AEDS in the presence of slow relaxing processes. We show that AEDS is able to successfully sample the relevant degrees of freedom, providing accurate binding free energies, without the need of previous information of the system in the form of collective variables. Additionally, we showcase the capabilities of AEDS to efficiently screen a set of ligands. These results represent a promising first step toward the development of free-energy methods that can respond to more intricate molecular events.
Project description:Capillary blood collection presents advantages such as reduced invasiveness over venous serum for syphilis diagnosing. This study aimed to compare diagnostic accuracy between capillary and venous blood samples for syphilis diagnosis. Individuals aged ≥ 18 years were included in a cross-sectional study. Syphilis screening was done using Rapid tests (RT) followed by collection of serum capillary and venous samples for VDRL and TPHA test. Sensitivity, specificity, and Kappa coefficient were calculated. Of 191 participants, 115 RT + and 76 RT-. Diagnostic properties did not significantly differ between capillary and venous samples. Capillary VDRL showed 99% sensitivity and 100% specificity, mirroring TPHA results. Furthermore, there was significant agreement between sample types for both serological tests (p < 0.001). Capillary sampling offers comparable diagnostic accuracy to venous collection, regardless of serum quality. Capillary sampling holds promise, particularly in developing countries and large-scale testing initiatives.
Project description:The goal of this study is to determine the feasibility of CEA assessments at home using (automated) capillary sampling in patients in the follow-up after treatment for colorectal cancer.
The main questions it aims to answer are:
* To determine the success rate of capillary sampling at home by the patient
* To assess reliability and satisfaction of (automated) capillary CEA measurements Participants will be asked to perform automated capillary sampling and lancet capillary sampling at home twice after regular check-up visits in the hospital, with an interval of 3-6 months in between. During this hospital visit, a CEA measurement in blood sampled by venipuncture will be performed to act as a reference for the CEA measurements in (automated) capillary blood to be sampled at home.
Reliability of CEA measurements will be assessed for automated capillary and lancet capillary sampling compared to venipuncture.
Satisfaction in terms of patient reported outcomes (pain, burden, ease of use, and preference) will be evaluated.
Project description:Capillary dilatometry enables direct measurement of changes in volume, an extensive thermodynamic property. The results provide insight into the changes in hydration that occur upon protein folding, ligand binding, and the interactions of proteins with nucleic acids and other cellular components. Often the entropy change arising from release of hydrating solvent provides the main driving force of a binding reaction. For technical reasons, though, capillary dilatometry has not been as widely used in protein biochemistry and biophysics as other methods such as calorimetry. Described here are simple apparatus and simple methods, which bring the technique within the capacity of any laboratory. Even very simple results are shown to have implications for macromolecular-based phenomena. Protein examples are described.
Project description:AimsThis multicenter prospective cohort study (registration no. ChiCTR2000032089) aimed to investigate the relationship between saliva and plasma levetiracetam concentrations to determine whether saliva could be used for routine monitoring of levetiracetam during pregnancy.MethodsThe slot concentrations of levetiracetam in simultaneously obtained saliva and plasma samples were measured using UPLC-MS/MS. The correlations between saliva and plasma levetiracetam concentrations and the dose-normalized concentrations were compared among pregnant women in different stages and nonpregnant control participants with epilepsy.ResultsIn total, 231 patients with 407 plasma and saliva sample pairs were enrolled from 39 centers. Linear relationships between salivary and plasma levetiracetam concentrations were reported in the enrolled population (r = 0.898, p < 0.001), including pregnant (r = 0.935, p < 0.001) and nonpregnant participants (r = 0.882, p < 0.001). Plasma concentrations were moderately higher than saliva concentrations, with ratios of saliva to plasma concentrations of 0.98 for nonpregnant women, 0.98, 1, and 1.12 for pregnant women during the first trimester, the second trimester, the and third trimester, respectively. The effective range of saliva levetiracetam concentration was found to be 9.98 μg/mL (lower limit) with an area under the curve (AUC) of 0.937 (95% confidence intervals, 0.915-0.959), sensitivity of 88.9%, specificity of 86.8%, and p < 0.001, to 24.05 μg/mL (upper limit) with an AUC of 0.952 (0.914-0.99), sensitivity of 100%, specificity of 92.3%, and p = 0.007.ConclusionThe saliva/plasma concentration ratio of levetiracetam remains constant during pregnancy and is similar to that in non-pregnant individuals. Monitoring levetiracetam concentration in saliva during pregnancy should be widely promoted.
Project description:Human enteric viruses are responsible to cause several diseases, including gastroenteritis and hepatitis, and can be present in high amounts in sewage sludge. This study compared virus recovery efficiency of two feasible concentration methods used for detecting human adenovirus (HAdV), rotavirus species A (RV-A), norovirus genogroup II (NoV GII) and hepatitis A virus (HAV) in sewage sludge from an activated sludge process. Twelve sewage sludge samples were collected bi-monthly from January to July, 2011. Ultracentrifugation was compared with a simplified protocol based on beef extract elution for recovering enteric viruses. Viruses were quantified by quantitative real-time PCR assays and virus recovery efficiency and limits of detection were determined. Methods showed mean recovery rates lower than 7.5%, presenting critical limits of detection (higher than 10(2) - 10(3) genome copies - GC L(-1) for all viruses analyzed). Nevertheless, HAdV were detected in 90% of the analyzed sewage sludge samples (range: 1.8 × 10(4) to 1.1 × 10(5) GC L(-1)), followed by RV-A and NoV (both in 50%) and HAV (8%). Results suggesting that activated sludge is contaminated with high viral loads and HAdV are widely disseminated in these samples. The low virus recovery rates achieved, especially for HAV, indicate that other feasible concentration methods could be developed to improve virus recovery efficiency in these environmental matrices.
Project description:Preliminary evidence indicates that people's sexual consent (i.e., their willingness to engage in sexual activity and communication of that willingness) varies across time and context. Study designs that assess sexual consent at multiple time points (e.g., experience sampling methodology [ESM]) are needed to better understand the within-person variability of sexual consent. However, extant validated measures of sexual consent are not appropriate for ESM studies, which require shorter assessments due to the increased burden this methodology has on participants. As such, the goal of the present study was to develop ESM measures of sexual consent based on items that have previously been validated for use in cross-sectional surveys. We selected items that balanced face validity as evidenced by cognitive interviews (n = 10) and content validity as evidenced by experts' ratings (n = 6). To assess the construct validity and feasibility of these items, we administered the selected ESM measures of sexual consent in a seven-day pilot study (n = 12). The results suggested that the ESM measures developed in the present study were a valid and feasible assessment of people's experience-specific internal consent feelings and external consent communication. We conclude with recommendations for sex researchers interested in ESM.
Project description:Serological testing is emerging as a powerful tool to progress our understanding of COVID-19 exposure, transmission and immune response. Large-scale testing is limited by the need for in-person blood collection by staff trained in venepuncture, and the limited sensitivity of lateral flow tests. Capillary blood self-sampling and postage to laboratories for analysis could provide a reliable alternative. Two-hundred and nine matched venous and capillary blood samples were obtained from thirty nine participants and analysed using a COVID-19 IgG ELISA to detect antibodies against SARS-CoV-2. Thirty eight out of thirty nine participants were able to self-collect an adequate sample of capillary blood (≥ 50 µl). Using plasma from venous blood collected in lithium heparin as the reference standard, matched capillary blood samples, collected in lithium heparin-treated tubes and on filter paper as dried blood spots, achieved a Cohen's kappa coefficient of > 0.88 (near-perfect agreement, 95% CI 0.738-1.000). Storage of capillary blood at room temperature for up to 7 days post sampling did not affect concordance. Our results indicate that capillary blood self-sampling is a reliable and feasible alternative to venepuncture for serological assessment in COVID-19.